There's always a lot on the line when a fighter steps into the cage. For starters, there's not a more personal contest in all of sports. Stripped to the waist and all alone, each athlete confronts his worst fears and his own mortality. And, oh yeah, a powerful and dangerous opponent in the opposite corner, one just as crazy and brave as he is.
At best, he's bathed in glory, one step away from a demi-god.
At worst?
He leaves on stretcher. If he's lucky.
As if that's not enough, in the UFC, even more is typically at stake. Money. It's the greatest motivator of them all, fungible, tangible and oh, so spendable. Most fighters can double their pay with a victory.
For some, that can be the difference between being a full-time professional athlete or a spending the summer on the construction crew waiting for the next call from UFC matchmaker Joe Silva. Many of these guys aren't fantasizing about building a beach house in Malibu after a big win. They're just trying to make rent and fund the next fight. 
Understand why their stomachs may be in knots before a bout?
And then there's Roy Nelson. The UFC heavyweight walked into Winnipeg for UFC 161 playing a high-stakes game with UFC president Dana White and owner Lorenzo Fertitta. It was the last fight on his deal. He had turned down an new contract worth six figures a fight. This fight, and this fight only, was all the security he had in this world. After almost a decade in the sport, he was paid just $24,000 to step into the cage.

By going out with a big win, Nelson figured he'd be in the catbird seat, able to play the UFC off rival Bellator Fighting and reap big benefits. Instead, he lost in embarrassing fashion, getting outclassed and out-punched by the lightly regarded Stipe Miocic.
Nelson thought he'd come to the table with a pair of aces. Now, after making it so evident to fans he isn't a top flight fighter, he's got a three and a five—off suited.
"We asked for an extension; he said no," White told the media after the event. "We made an offer to Roy. And we'll sit down again after this."
Somehow, I suspect, the positions will be reversed this time around. Nelson now owns the dubious distinction of absorbing more significant strikes than any fighter in UFC history. But will promotions pay big for a glorified punching bag?
"The good thing is the fans in Winnipeg got their money’s worth,” Nelson told Fuel TV after the fight.
That's certainly one way of looking at it.
Others might point out that Nelson, belly jiggling over the waistband of his shorts, came into the bout in even worse shape than usual. That he wasn't capable of fighting more than a single round before heaving for breaths and only occasionally winging a big right hand. That he actually cheated the fans out of a competitive fight because thanks to a combination of lifestyle choices and pure stubbornness.
"I've got to breathe," Nelson said, describing the experience to Fuel's Ariel Helwani. "Wait, no, I'm getting hit."